1. Field
This document relates to a display device, and more specifically to a touch sensor integrated display device.
2. Related Art
A touch sensor is a kind of input unit which is mounted on a video display device, such as a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), an electroluminescence device (ELD), electrophoresis display (EPD), and so forth. While an image is displayed by the video display device, a user may contact, by pressing or touching, a touch panel on the video display device to input predetermined optional information through the touch sensor mounted in the video display device.
Touch sensors used for display devices as described above may be largely divided into an add-on type, an on-cell type, and an integrated type, according to structures thereof. In the case of an add-on type touch sensor, after a display device and the touch sensor have been manufactured in separate processes, respectively, the manufactured touch sensor is attached on the top plate of the display device. In the case of an on-cell type touch sensor, component parts constituting the touch sensor are directly formed on a surface of a top glass substrate on a display device. In the case of an integrated type touch sensor, the touch sensor is built in a display device to attain a thinner display device and improve durability.
The add-on type touch sensors, however, have some disadvantages in that display devices having the touch sensors become thick because the touch sensors are disposed on the display devices in the form of completely-finished products and in that the brightness of the display devices tend to be lowered, which deteriorates Visibility of the display devices. Further, display devices having the on-cell type touch sensors are relatively thinner than display devices having the add-on type touch sensors because separate touch sensors are formed on top surface of the display device. The display devices having the on-cell type touch sensors, however, have some disadvantages in that the entire thickness of the display devices becomes thicker and in that not only the number of processes but also manufacturing costs of the display devices are relatively higher because of driving electrode layers and sensing electrode layers constituting the touch sensors, and insulating films for insulating those electrode layers.
On the other hand, the integrated type touch sensors have some advantages in that they can realize substantially thinner display devices and improve durability, and thus, overcome the disadvantages of the display devices having the add-on type and the on-cell type touch sensors. Integrated type touch sensors include optical types, electrostatic capacity types, and so forth.
In the case of the optical type touch sensors, an optical sensing layer is formed on thin transistor substrate arrays of a display device. An object touching the optical sensing layer can be recognized through light reflected on the object by using light from a back light unit or infrared ray light. The optical type touch sensors can be normally and safely operated under dark surroundings, and surrounding light can act as a noise when the surrounding light is brighter than the reflected light from the object. For example, light reflected from the object has very low brightness so that even under slightly bright surroundings, touch recognition errors can occur. Especially, under very bright sun light, touch recognition by the optical type touch sensor may not operate normally.
The electrostatic capacity type touch sensors include a self capacitance type and a mutual capacitance type. In the case of the mutual capacitance type, a common electrode for display is divided into a driving electrode area and a sensing electrode area, and a mutual capacitance is formed between the driving electrode area and the sending electrode area so that a variation in mutual capacitance generated on touching can be measured to recognize the touching operation based on the measured values.
The mutual capacitance type touch sensors, however, have some disadvantages in that it is difficult to exactly recognize touched spots because the mutual capacitance generated on touching recognition is very small while parasitic capacitance between gate lines and data lines is relatively very large. The gate lines and the data lines are constitutional elements of the display device.
Furthermore, the mutual capacitance type touch sensors require very complex circuit wiring structures because many touch driving lines for touch driving and many touch sensing lines for touch sensing should be formed on the common electrode to obtain multi-touch recognition.
Accordingly, there exists a demand for a new type of touch sensor integrated display device for solving the problems of the above-mentioned prior art touch sensors.